Change PaintLayer::m_layoutObject to a reference.

third_party/WebKit/Source/core/paint/PaintLayerStackingNode.h

 /*
  * Copyright (C) 2003, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Intel Corporation. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
@@ skipping 80 matching lines @@
 // A real stacking context can also be a leaf if it doesn't contain any stacked
 // elements.
 class CORE_EXPORT PaintLayerStackingNode {
   USING_FAST_MALLOC(PaintLayerStackingNode);
   WTF_MAKE_NONCOPYABLE(PaintLayerStackingNode);
 
  public:
   explicit PaintLayerStackingNode(PaintLayer*);
   ~PaintLayerStackingNode();
 
-  int zIndex() const { return layoutObject()->style()->zIndex(); }
+  int zIndex() const { return layoutObject().style()->zIndex(); }
 
   bool isStackingContext() const {
-    return layoutObject()->style()->isStackingContext();
+    return layoutObject().style()->isStackingContext();
   }
 
   // Whether the node is stacked. See documentation for the class about
   // "stacked".  For now every PaintLayer has a PaintLayerStackingNode, even if
   // the layer is not stacked (e.g. a scrollable layer which is statically
   // positioned and is not a stacking context).
   bool isStacked() const { return m_isStacked; }
 
   // Update our normal and z-index lists.
   void updateLayerListsIfNeeded();
@@ skipping 54 matching lines @@
     m_stackingParent = stackingParent;
   }
 #endif
 
   bool isDirtyStackingContext() const {
     return m_zOrderListsDirty && isStackingContext();
   }
 
   PaintLayerCompositor* compositor() const;
   // We can't return a LayoutBox as LayoutInline can be a stacking context.
-  LayoutBoxModelObject* layoutObject() const;
+  LayoutBoxModelObject& layoutObject() const;
 
   PaintLayer* m_layer;
 
   // m_posZOrderList holds a sorted list of all the descendant nodes within
   // that have z-indices of 0 (or is treated as 0 for positioned objects) or
   // greater.
   std::unique_ptr<Vector<PaintLayerStackingNode*>> m_posZOrderList;
   // m_negZOrderList holds descendants within our stacking context with
   // negative z-indices.
   std::unique_ptr<Vector<PaintLayerStackingNode*>> m_negZOrderList;
@@ skipping 55 matching lines @@
 
  private:
   PaintLayerStackingNode* m_stackingNode;
   bool m_previousMutationAllowedState;
 };
 #endif
 
 }  // namespace blink
 
 #endif  // PaintLayerStackingNode_h